Martedì 9 Ottobre 2018 alle ore 11.30

AULA CALCOLO, Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, P.le Tecchio

il Dott.  Francesco TURCI - H.H. Wills Physics Laboratory, University of Bristol

terrà un seminario dal titolo:
    

   "Structural-dynamical transitions in glass-forming systems"

Abstract

Glass-forming liquids are examples of frustrated systems: their characteristically slow dynamics and high viscosities are often thought as being linked to the impossibility for the constituents to satisfy local geometrical constraints at a global scale [1]. Starting from experimental evidence in colloidal glasses, I will show that an analysis of local geometrical motifs in real space allows us to identify signatures of an emergent non-crystalline local order in an exceptionally deeply supercooled regime [2]. Such increase of multi-body correlations in the supercooled regime can be predicted thanks to a purely geometrical (morphometric) framework [3]. However, to relate this to the slow dynamics and frustration of glasses, I will rationalise the experimental evidence with numerical models studied within the framework of large deviations of structural-dynamical observables [4]. First, I will discuss the general ideas of the framework and show that an accurate measure of fluctuations of structural correlations in trajectories contains deep dynamical and thermodynamical information on very low temperature equilibrium states.Then, I will show that, for three distinct models of glass-formers analysed within this framework [4,5,6], slow dynamics corresponds to the coexistence of structure-rich/poor phases in an augmented dynamical space, with a non-trivial temperature dependence that allows us to reinterpret a variety of scenarios for the low-temperature behaviour of supercooled liquids in terms of amorphous-to-amorphous transitions.

[1] F Turci, G Tarjus, CP Royall, Phys. Rev. Lett. 118, 215501, (2017)

[2] JE Hallett, F Turci, CP Royall, Nature Communications 9, 3272 (2018)

[3] JF Robinson, F Turci, R Roth, CP Royall, Submitted to Phys. Rev. Lett. arXiv:1809.02401 (2018)

[4] F Turci, CP Royall, T Speck, Phys. Rev. X 7, 031028 (2017)

[5] R. Pinchaipat et al., Phys. Rev. Lett. 119, 028004, (2017)

[6] F Turci T Speck and CP Royall, Eur. Phys. J. E , 41: 54 (2018)